ASTM International, formerly known as the American Society for Testing and Materials (ASTM), is a globally recognized leader in the development and delivery of international voluntary consensus standards. Today, some 12,000 ASTM standards are used around the world to improve product quality, enhance safety, facilitate market access and trade, and build consumer confidence.

Standards:

D-445 determines an oil’s viscosity of fluidity at a specific temperature. At the same temperature, a light ISO 32 oil has a lower viscosity than a heavier ISO 150 oil. When the temperature changes, the viscosity of each oil will change. When an oil’s temperature increases it becomes more fluid, or thinner; When it temperature drops it becomes less fluid, or thicker. The oil temperature must always be given when reporting a viscosity. The three most common temperatures
used to report viscosities are 40ºC, 100ºC and the oil’s operating temperature. Oil viscosity is expressed in either SUS (Saybolt Universal Seconds) or in cSt (centistokes). Centistoke viscosity is an international standard and is more widely used.

D-2270 determines the Viscosity Index (VI) of an oil. It is an empirical number used to measure an oil’s ability to resist viscosity changes when the temperature changes. High VI oils have smaller viscosity changes than low VI oils when the temperature changes. Viscosity Index cannot be used to measure any other quality of an oil.